The conventional method of butchering hogs does not contemplate the removal of the hide or skin prior to the butchering operations, but the hog, after killing, is carried through a series of operations designed to remove the hair and bristles and to thoroughly clean the outer skin surface of the hog carcass. In the conventional procedures, substantially all of the skin or hide remains on the hog during the killing operation and throughout most of the butchering operation.
In order to prepare the carcass for the conventional dehairing operation, the carcass is first scalded by placing it in a tank of hot water (at temperatures of from 135.degree. to 145.degree. F.) for about 5 minutes. The purpose of the scalding tank is simply to loosen up the hair of the hog to prepare the carcass for the dehairer. As is explained below, the hogs move through the slaughtering operation at speeds up to 1440 feet per hour, which requires the scalding tank to be at least 120 feet long. The installation of such a tank represents a substantial investment and the operation is costly in terms of the overall maintenance and the heat requirement necessary to keep the water at the requisite temperatures. Further, disposal of the water from the tank represents a serious pollution problem.
After the carcasses have been scalded in the tank, they are conveyed to a dehairing machine which comprises a series of rubber paddles which beat most of the loosened hair from the carcass. The next step in the conventional dressing method is to singe the carcass in a gas flame. The purpose of the gas flame is to burn off the remaining hair. The operation of the dehairing and singeing equipment is extremely costly since the equipment required is expensive and it requires substantial floor space as well as requiring continuing maintenance. Further, since Federal regulations require that all equipment in packing houses be cleaned and sterilized on a daily basis, the maintenance of these machines requires a great deal of labor and consequently is very expensive. In addition to requiring a substantial quantity of fuel, the fumes from the singeing apparatus are pungent and offensive, and represent another pollution problem.
Following the singeing operation, the carcasses are shaved to remove the last traces of hair and bristles. Since the carcasses vary in size substantially from one to another, it is necessary that the shaving operation be done by hand. In a typical operation, as many as eight men are required to accomplish the shaving operation. In some cases the bristles are sufficiently tough that portions of the skin or hide must be actually cut away.
Following the shaving operation, the carcass is washed and is then ready for the butchering operation whereby the carcass is opened up. The conventional butchering operations which follow the cleaning of the hide include removal of the head, evisceration, splitting the carcass, and inspection of the carcass, which may take place in several stages.
Following the evisceration and splitting operations, in the conventional process, the split carcasses are chilled for a period of 12 to 20 hours in order to lower the internal carcass temperature to approximately 36.degree.-38.degree. F., the temperature necessary to firm up the meat and permit the carcass to be cut into primal cuts, after which various portions are skinned according to the need.
In the butchering and dressing of hogs and other such animals, it is common to suspend the animals in the normal head-down position by their hind feed or legs by means of hooks called gambrels. The gambrels are swivelly mounted on trolleys located on overhead tracks which lead through the various butchering operations. The trolleys, and in turn the animals, are moved along the overhead track by a mechanism such as a chain conveyor having pusher plates depending therefrom, which plates push the trolleys about the killing and dressing rooms. In this manner, the animals are moved in a continuous stream to the stations in the plant where the various butchering operations are performed. In a hog butchering plant, the animals are typically hung on two foot centers, which leaves adequate space for the various butchering operations to be performed. To be commercially attractive, such plants must be capable of handling up to 770 hogs per hour, so that it is desirable that the conveyor move at a maximum speed of up to 1440 feet per hour.
It is obviously desirable to dress as many carcasses as possible within a given period of time, since the unit cost to dress a given carcass will decrease with any increase in the number of carcasses dressed in any given period of time. It therefore follows that if the conveyor is stopped or slowed during any station of the operation, the total number of carcasses dressed in a given period of time will be decreased.
One of the operations in a packing plant which typically causes bottlenecks is the cleaning and dehairing operation.
Recently, machinery has been devised to remove the skin from a hog carcass in substantially one piece while the hog carcass is suspended or moving along a conveyor (See U.S. Pat. Nos. 3,209,395; 3,621,514; and 3,423,789). In addition to eliminating the conventional scalding and dehairing operation, a skinning operation which does not scald produces a hide which is a good leather and is far more valuable than the hide from a scalded animal. Most of these prior art patents describe the skinning of hogs while the carcasses are suspended in the normal head-down position by the hind legs. Since the conventional head-down attitude is used in the sticking or bleeding operation, the prior art apparatus has simply left the carcass in the head-down attitude and devised various types of apparatus designed to skin the carcass while it was in this attitude.
Since it is difficult and impractical to skin a hog by drawing the skin from the butt end toward the head, most of the prior art devices which have significant commercial promise accomplish the skinning by pulling the hide from the head end of the carcass toward the butt end of the carcass. In order to remove the hide from the carcass while the carcass is in the head-down position, it is necessary to secure the carcass, both by head and foot (butt-end or hind feet suspension), followed by drawing the hide from the head toward the butt in a substantially upward, vertical, direction. However, when hogs, or other animals enter a packing plant, their hides are normally covered with a substantial amount of dirt, loose hair, manure, and the like which has been picked up during transportation and storage in the stockyard pen. If the animal is not dehaired and cleaned prior to the dehiding operation, the dirt, hair and other contaminants have a tendency to fall onto the stripped carcass as the hide is being pulled upwardly. When the hide is finally freed from the carcass, the release is frequently accompanied by a shower of dirt, hair, and other debris which falls around and onto the skinned carcass. This dirt is very difficult to remove from the dehided carcass and usually requires either separate step to wash or otherwise remove the dirt from the fat remaining with the carcass, or the outer layer of the fat is trimmed away and is relegated to nonedible uses.